cmake: Fix relative paths for add_custom_{command,target}

Do this by tracking CMAKE_CURRENT_{SOURCE,BINARY}_DIR variables.
This is achieved by injecting CMake code with CMAKE_PROJECT_INCLUDE
and overriding some builtin functions with a wrapper that adds
additional trace information.

1 files changed, 35 insertions, 0 deletions

diff --git a/mesonbuild/cmake/data/preload.cmake b/mesonbuild/cmake/data/preload.cmake
new file mode 100644
index 000000000..30178fba5
--- /dev/null
+++ b/mesonbuild/cmake/data/preload.cmake
@@ -0,0 +1,35 @@
+if(MESON_PS_LOADED)
+  return()
+endif()
+
+set(MESON_PS_LOADED ON)
+
+# Dummy macros that have a special meaning in the meson code
+macro(meson_ps_execute_delayed_calls)
+endmacro()
+
+macro(meson_ps_reload_vars)
+endmacro()
+
+# Helper macro to inspect the current CMake state
+macro(meson_ps_inspect_vars)
+  set(MESON_PS_CMAKE_CURRENT_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}")
+  set(MESON_PS_CMAKE_CURRENT_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}")
+  meson_ps_execute_delayed_calls()
+endmacro()
+
+
+# Override some system functions with custom code and forward the args
+# to the original function
+macro(add_custom_command)
+  meson_ps_inspect_vars()
+  _add_custom_command(${ARGV})
+endmacro()
+
+macro(add_custom_target)
+  meson_ps_inspect_vars()
+  _add_custom_target(${ARGV})
+endmacro()
+
+set(MESON_PS_DELAYED_CALLS add_custom_command;add_custom_target)
+meson_ps_reload_vars()